Interestingly, and I admit my knowledge is limited on this, lens resolution/performance can vary with focusing/subject distance, and annoyingly this factor is rarely mentioned or tested by many lens testing sites. My 17-40 and EF-S 10-22 are both similar in this regard on the 7D, at close distances even to the edges of the frame the sharpness is pretty good, but for infinity subjects at the corner of the frame it's a different matter. Obviously, factors such as CA, field curvature and astigmatism have a part to play, and resolving fine detail on small and distant subjects is always going to be a bigger test of a lens than closer subjects.

It's always going to be better on an APS-C body like the 7D over a full frame body...

Agreed, but the point about some lenses performing better at closer focus distances than infinity should apply equally to crop or full frame.

I almost thought the lens was defective, actually, until I examined some of the shots I took at closer distance....weird.

This doesn't seem to be mutually exclusive to me - while it's true lenses show different sharpness depending on focus distance, the effect on your particular copy of the lens could very well be stronger than the average "standard" due to a defect or simply bad luck with a "bad copy".

I do a lot of city shots at night, I can tell you that the 17-40 has the best flare control of any lens I've ever used. Both for controlling artifacts and veiling flare. If your looking for resolution mostly, I'd look at the Tokina 16-28. I tried the 16-35 II and found it wasn't as good in contra light as the 17-40 and not as sharp as the Tokina, but it was second best at both.

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I'd look at the Tokina 16-28.

Mine just came in yesterday, virtually worthless at f/2.8 for anything sharp. Also, focus motor is quite loud. I can live with that but when focussing from wide to narrow or visa versa, there is almost a grinding sound! Doesn't sound good at all, I can only picture little pieces of plastic or metal being ground down inside the lens body! The terrible sharpness at f/2.8 and the grinding noise will win this Tokina a place in the return mail! I will let them send me a new copy as I noticed the barrel distortion was really slight, even wide open at 16mm. That part was pretty impressive.

If the new copy fixes the sharpness issue at f/2.8 and the grinding sound coming from the AF, I'll keep it. If not, I'll be sending it back and moving toward the Canon ef 16-35 f/2.8 II.

Also, the Tokina lens is very heavy. I have a lot of heavy lenses but this one seems very heavy for it's relatively small size... I'll have it mostly on a tripod so that won't matter to much to me...

The vignetting was fairly normal to heavy at f/2.8 but it was extremely minimal at f/4.0 and above. Very pleased with that. CA was the same, very well under control... Hopefully, given the sharpness issue and the grinding, I just got an ill copy...

I can add the filter system to it and still be well under the cost of the EF 16-35mm II

@ Krob78: bad luck, you have got a bad copy.I had a hard time even thinking about buying a third party lens, after using almost 30 years only Canon.The drive is louder, but extra sound like you described seems to be a serious damage.I have read many reviews on the net before buying, Tokina seems to have issues with quality control.So I choosed to order it from a place, where I can send it back with no problems.I wish you good luck with the replacement.

@ Krob78: bad luck, you have got a bad copy.I had a hard time even thinking about buying a third party lens, after using almost 30 years only Canon.The drive is louder, but extra sound like you described seems to be a serious damage.I have read many reviews on the net before buying, Tokina seems to have issues with quality control.So I choosed to order it from a place, where I can send it back with no problems.I wish you good luck with the replacement.

Thanks Alex, I did send it back however I decided not to opt for a replacement. Although it was mostly good, the weight was really absurd and I decided I didn't want to "try" another one, so I ended up with another Canon L lens... I picked up a 17-40mm L and it works great, just like I knew it would. Surprisingly and conversely, the 17-40mm L is amazingly light!! Almost too light for my liking!!

But no flare issues, nice color rendering, sharp. Price was excellent at only $625 for brand new in box. I use it mostly for interior Real Estate work, so f/4 isn't an issue as I'm shooting it primarily indoors at f/5.6 and f/8. A little wider would have been nice but the lens will pay for itself very quickly with a couple of shoots.

I wanted the 16-35mm f/2.8 but decided with rumors of a new wide angle being announced later this year (hopefully with IS), I decided to pocket the almost $800 difference and I'll take a look at the new offering when it comes out... If it doesn't surface, I'll think about upgrading at that time. For now, other than the amazing lightness (feels cheap), of the 17-40mm, I'm set...